The horse’s diet is made up of a number of constituents from which energy can be derived, including Gross energy, Digestible energy, Metabolisable energy, and Net energy.
Gross Energy (GE)
Describes the total energy contained within a feed. It is measured as the heat given off when the feed is burned in a bomb calorimeter.
Digestible Energy (DE)
Digestible energy is the gross energy of a feed, minus the energy content of the faeces attributable to it. (Frape, 2004)
Metabolisable Energy (ME)
The metabolisable energy of a food is the digestible energy less the energy lost in the urine and combustible gases.
Net Energy (NE)
The deduction of the heat increment of food from its metabolisable energy gives the total of net energy value.
‘Heat increment’ – can be defined as the heat loss of a nourished animal in excess of that lost by a fasting animal. (Frape, 2004).
Figure 1 below illustrates these terms.